If you wanted to use MailChimp, you could use my MailChimp Integration for this. MailChimp includes the ability to edit the "welcome" e-mail sent to customer's after signing up, so you could put your coupon code there, and the customer would get it after subscribing.

It also includes the ability to show a pop-up modal for signing up, when customers first visit your site. You can edit the pop-up with some HTML code, or by editing the .tpl file.

There are other benefits for using MailChimp for your e-mail marketing, such as reducing server load from your server sending out e-mails, and better templates / campaign design, so it's worth considering if you haven't already. Their free account remains free up to 2,000 subscribers, I believe.

Feel free to take a look at the screenshots and demo site, and if you're interested let me know at www.getclearthinking.com/contact if you have any further questions.

Thank you, Johnathan - I did purchase your MailChimp Integration extension, and I did not know it had those features! How can I edit the HTML for the modal popup? Where do I edit the Welcome email template in MailChimp?

Thanks for your purchase. Please contact me with your order number at the e-mail address in the extension files, or the "contact" link in the extension description, for support with extension issues.

You can add HTML for the module in any of the fields that support HTML content. For example, the "Top Text" field might be a good spot. If you need more flexibility than that, and want to edit the template file directly, you can do that in this file:

/catalog/view/theme/default/template/module/mailchimp_integration.tpl

For editing the Welcome e-mail, you can do that in your List's "Signup Forms" area.

Hi, we see your good module. Btw, we need mailchip really, but the issue the double-opt option. Your module can disable this via api calling or built it with already? (the option to disable double-opt in) where the customer just key in the email and it will deliver to the list (without the customer going to confirm it).